Top corner rounding of damascene wire for insulator crack suppression

ABSTRACT

A structure and method for fabricating the structure that provides a metal wire having a first height at an upper surface. An insulating material surrounding said metal wire is etched to a second height below said first height of said upper surface. The metal wire from said upper surface, after etching said insulating material, is planarized to remove sufficient material from a lateral edge portion of said metal wire such that a height of said lateral edge portion is equivalent to said second height of said insulating material surrounding said metal wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit under 35 U.S.C. §120 as adivisional of presently pending U.S. patent application Ser. No.13/304,772 entitled “TOP CORNER ROUNDING OF DAMASCENE WIRE FOR INSULATORCRACK SUPPRESSION”, filed on Nov. 28, 2011, the entire teachings ofwhich are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention generally relates to a method and correspondingstructure that prevents insulator cracking at a corner or edge of anon-planar damascene metal wire.

2. Background

Insulator cracking at the corner or edge of non-planar damascene wire isa common problem in semiconductor fabrication where the metal wireinductor structures are relatively thick, (>3 microns), and thesurrounding adjacent insulating materials, (e.g., silicon dioxide,SiO₂), are relatively brittle. Since the metal inductors andcorresponding insulators have a significant mismatch in theircoefficient of thermal expansion, e.g., a copper (Cu) inductor may havea coefficient of thermal expansion of approximately twenty (20) timesthat of the coefficient of thermal expansion of a SiO₂ insulator, themismatch in coefficients of thermal expansion typically causes the morebrittle insulator to crack at stress risers located on the inductor.These stress risers are usually located at corner portions of the metalinductors that occur at discrete layers of a damascene metal structureduring the fabrication of the entire non-planar damascene metalinductor.

Advanced analog and mixed-signal applications require these metalinductor layers and are typically fabricated in matching networks forvery high frequency applications. However, for high quality inductorswith low resistive losses, the inductor thickness is typically muchgreater than interconnect wiring. Thus, to achieve the designrequirements of low resistive losses, the metal damascene inductors arerelatively large in size with respect to the surrounding insulatormaterial, and therefore, have a higher propensity of causing crackingdue to stress build-up between the two thermally-mismatched materials.

BRIEF SUMMARY

According to one example, a method herein provides a metal wire having afirst height at an upper surface. An insulating material surrounding themetal wire is etched to a second height below the first height of theupper surface. The metal wire from the upper surface is planarized,after etching the insulating material, to remove sufficient materialfrom a lateral edge portion of the metal wire such that a height of thelateral edge portion is equivalent to the second height of theinsulating material surrounding the metal wire. A central portion of themetal wire, opposite the lateral edge portion, extends to a third heightabove the second height.

According to another example, another method provides planarizing ametal wire to a first height at an upper surface. An oxide materialsurrounding the metal wire is etched to a second height below the firstheight at the upper surface. The metal wire is planarized at the uppersurface, after the etching the oxide material, to remove sufficientmaterial from a lateral edge portion of the metal wire such that aheight of the lateral edge portion is equivalent to the second height ofthe oxide material surrounding the metal wire. A central portion of themetal wire, opposite the lateral edge portion, extends to a third heightabove the second height.

According to another example, a structure provides a metal wire having afirst height at a central portion, a second height at a first distaledge less than the first height, and a radius defined from the secondheight at the first distal edge to the first height at the centralportion. In addition, an insulating material surrounds the metal wire tothe second height at the first distal edge of the metal wire. The firstheight of the metal wire extends above the second height of the firstdistal edge and the insulating material.

According to another example, a structure provides a non-planardamascene metal wire having a first height at a central portion, asecond height at a first distal edge less than the first height, and aradius defined from the second height at the first distal edge to thefirst height at the central portion. In addition, an oxide materialsurrounds the non-planar metal wire to the second height at the firstdistal edge of the metal wire. The first height of the non-planardamascene metal wire extends above the second height of the first distaledge and the oxide material.

With these features, the embodiments herein may provide a structure andmethod of providing the structure that produces a radius where a cornerportion of a non-planar metal damascene wire used to be by a secondarysoft-pad chemical mechanical planarization process to eliminate thestress raiser of the sharp corner portion of the metal inductor formedthough a previous fabrication process.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other exemplary purposes, aspects and advantages willbe better understood from the following detailed description of anexemplary embodiment herein with reference to the drawings.

FIG. 1A is a top view of a schematic diagram of a cracked insulatormaterial proximate a non-planar damascene metal wire;

FIG. 1B is a cross sectional view of section line A-A from FIG. 1A;

FIG. 2A is a cross sectional view of a schematic diagram of anembodiment illustrating a deposition of a portion of a non-planardamascene metal wire;

FIG. 2B is a cross sectional view of a schematic diagram of theembodiment illustrating a process of Chemical Mechanical Planarization(CMP) of a top portion of the non-planar damascene metal wire;

FIG. 3 is a cross sectional view of a schematic diagram of theembodiment illustrating a process of etching a portion of insulatormaterial below the top portion of the non-planar damascene metal wire;

FIG. 4A is a cross sectional view of a schematic diagram of theembodiment illustrating a process of CMP material removal of an edgeportion of the non-planar damascene metal wire proximate the insulatormaterial;

FIG. 4B is an alternative embodiment of the cross sectional view of FIG.4A illustrating an alternative profile of CMP material removal of theedge portion of the non-planar damascene metal wire;

FIG. 5A is a top view of a schematic diagram of one embodimentillustrating a geometry of a non-planar damascene metal wire;

FIG. 5B is a top view of a schematic diagram of another embodimentillustrating a linear geometry of a non-planar damascene metal wire; and

FIG. 6 a logic flowchart of a method for an embodiment described herein.

DETAILED DESCRIPTION

Referring now to the drawings, and more particularly to FIGS. 1A-6,there are shown exemplary embodiments of the method and structures ofthe embodiments herein.

FIG. 1A is a top view of a schematic diagram of a cracked insulatingmaterial proximate a non-planar damascene metal wire. A crack 14 ispropagated in an insulating material 12 proximate a non-planar damascenemetal wire 10 typical of a mismatched coefficient of thermal expansionbetween the two materials. For purposes herein, an “insulator” is arelative term that means a material or structure that allowssubstantially less (<95%) electrical current to flow than does a“conductor.” The dielectrics (insulators) mentioned herein can, forexample, be grown from either a dry oxygen ambient or steam and thenpatterned. Alternatively, the dielectrics herein may be formed from anyof the many candidate high dielectric constant (high-k) materials,including but not limited to silicon nitride, silicon oxynitride, a gatedielectric stack of SiO₂ and Si₃N₄, and metal oxides like tantalumoxide. The thickness of dielectrics herein may vary contingent upon therequired device performance. The metal wires mentioned herein can beformed of any conductive metal, such as copper, aluminum, tungsten,hafnium, tantalum, molybdenum, titanium, or nickel, or a metal silicide,any alloys of such metals, and may be deposited using physical vapordeposition, chemical vapor deposition, or any other technique known inthe art.

FIG. 1B is a cross sectional view of section line (A-A) from FIG. 1Athat illustrates the crack 14 propagating from an upper corner portionof the metal wire 10 that has damascene layers 10A, 10B and 10C.

FIG. 2A is a cross sectional view of a schematic diagram of anembodiment illustrating a deposition of a portion of a non-planardamascene metal wire 20, having damascene layers 20A, 20B and 20Cadjacent an insulating material 12, such as SiO₂. In a fabricationprocess, a layer of metal 20A, e.g., Cu, may be deposited on top of theinsulating material 12 and any underlying metal inductor layers, e.g.,20B and 20C.

FIG. 2B is a cross sectional view of a schematic diagram of theembodiment illustrating a process of a hard-pad Chemical MechanicalPlanarization (CMP) of a top portion of the non-planar damascene metalwire 20, such that the top portion of the metal layer 20A is removedfrom over the insulating material 12 as illustrated by reference number22. The CMP process creates a uniform top surface across the metal wire20 and the insulating material 12 as illustrated by the surface S havinga first height H1.

FIG. 3 is a cross sectional view of a schematic diagram of theembodiment illustrating a process of etching a portion 24 of theinsulating material 12 below the top surface S of the non-planardamascene metal wire 20, such that only the insulating material 12 isetched to a second height H2, below that of the top surface S of themetal wire 20 at the first height H1. That is, as shown in FIG. 3, thenon-planar damascene metal wire 20 remains at a height H1 and theinsulating material 12 is reduced to a height H2. This etching can beperformed by patterning a mask over the metal wire 20, or by performingselective etching using an etchant that does not attack metal. Whenpatterning any material such as a mask herein, the material to bepatterned can be grown or deposited in any known manner and a patterninglayer (such as an organic photoresist) can be formed over the material.The patterning layer (resist) can be exposed to some form of lightradiation (e.g., patterned exposure, laser exposure, etc.) provided in alight exposure pattern, and then the resist is developed using achemical agent. This process changes the characteristic of the portionof the resist that was exposed to the light. Then one portion of theresist can be rinsed off, leaving the other portion of the resist toprotect the material to be patterned. A material removal process is thenperformed (e.g., plasma etching, etc.) to remove the unprotectedportions of the material to be patterned. The resist is subsequentlyremoved to leave the underlying material patterned according to thelight exposure pattern.

FIG. 4A is a cross sectional view of a schematic diagram of theembodiment illustrating a second process of CMP material removal of acorner portion 26 of the non-planar damascene metal wire 20 proximatethe insulating material 12. The second CMP material removal processtapers the height of the corner portion 26 of the metal wire 20 suchthat distal edges 29 of the metal wire 20, opposite a central portion Cof the metal wire 20 are removed, and the height of the metal wire 20 atthe distal edges 29 is generally equivalent to the second height H2 ofthe etched insulating material 12 as shown in FIG. 3.

The second process of CMP material removal may be accomplished with awet etch insulator oxide recess and soft-pad metal CMP that allows for agreater amount of material to be removed from distal edges of metalwires than a central portion of the metal wires. The second CMP processmay utilize traditional copper CMP slurry, which usually combines anoxidizer such as Ferric Nitrate, and an abrasive such as Icue 600 asmanufactured by the Cabot Corporation in Aurora, Ill., or other copperslurries. Many types of CMP tools may be used, such as the Ebarra 222200 mm CMP clustered tool. The CMP process itself would use a Politexpolish pad as manufactured by Dow Chemicals (Semiconductor Division).CMP processing would utilize 2 to 4 Pascals of down force, with waferrotations of 50 to 150 revolutions-per-minute (RPM), polish pad rotationspeeds of 50 to 150 RPM, and polish times of 15 to 45 seconds. Theprocess is time-limited so as to round the corners of the metal wire 20without substantially over polishing the metal wire 20 itself.

As shown in FIG. 4A, after the second CMP material removal process, theheight of the metal wire 20 at the distal edges 29 of the metal wire 20may be substantially equivalent to the second height H2 of theinsulating material 12. The upper surface S of the metal wire 20 mayhave a height substantially equivalent to the first height H1, or aslightly lower height H3 substantially closer in height to the firstheight H1 than the second height H2 due a limited amount of materialremoval of the metal wire 20 from the upper surface S during the secondCMP process.

FIG. 4B is an alternative embodiment of the cross sectional view of FIG.4A illustrating an alternative/magnified profile of CMP material removalof the corner portion 26 of the non-planar damascene metal wire 20 thatdemonstrates a roughly flat portion F proximate the central portion C ofthe metal wire 20 with a corner portion 26 of the metal wire removedfrom the distal edges 29 that creates a curved portion having a radius Rbetween the distal edges 29 and either the flat portion F or the centralportion C of the metal wire 20. The resultant radius R of the metal wire20 eliminates any stress riser between the metal wire 20 and the morebrittle insulating material 12 preventing the initiation and subsequentpropagation of cracks through the insulating material 12 due to themismatch of coefficients of thermal expansion in the adjacent materials.Thereafter, an insulating material may be deposited over the top of themetal wire 20 and the adjacent insulating material 12.

FIG. 5A is a top view of a schematic diagram of one embodimentillustrating a geometry of a non-planar damascene metal wire 50 that islocalized at a specific point in a semiconductor being surrounded by aninsulating material 52. A flat portion 54 of the metal wire 50transitions to a radius 56 or tapered edge in the direction of the outeredge of the wire 50 at the interface of the insulating material 52.

FIG. 5B is a top view of a schematic diagram of another embodimentillustrating a non-planar damascene metal wire 60 having a lineargeometry L oriented in a direction perpendicular to the metal stack ofan inductor wire surrounded in the insulator material 62. A flat portion64 of the metal wire 60 transitions to a radius 66 or tapered edge inthe direction of the outer edge of the wire 60 at the interface of theinsulating material 62.

FIG. 6 is a logic flowchart of a method for an embodiment describedherein where a metal wire is provided having a first height at an uppersurface 600. An insulating material surrounding the metal wire is etchedto a second height below the first height of the upper surface 602. Themetal wire may be planarized from the upper surface, after etching theinsulating material 604. Removing sufficient material from a lateraledge portion of the metal wire such that a height of the lateral edgeportion is equivalent to the second height of the insulating materialsurrounding the metal wire 606. A central portion of the metal wire,opposite the lateral edge portion, may extends to a third height abovethe second height and substantially similar to the first originalheight.

Providing the metal wire (20) may further comprise depositing anon-planar damascene (20A, 20B, 20C) metal wire (20). The etching of theinsulating material (12) may further comprise etching an oxide material,e.g., SiO₂. The coefficient of thermal expansion of the metal wire (20)may be greater than 10 times a thermal coefficient of expansion of theinsulating material (12). The planarizing may further comprise soft-padChemical-Mechanical Polishing (CMP), where the planarizing the metalwire provides a radius (R) at the lateral edge portion (at 26) of themetal wire (20).

An embodiment presented herein includes a structure including a metalwire (20) having a first height (H1) at a central portion (C), a secondheight (H2) at a first distal edge (at 29) less than the first height(H1), and a radius (R) defined from the second height (H2) at the firstdistal edge (at 29) to the first height (H1) at the central portion (C).Additionally, an insulating material (12) surrounds the metal wire (20)to the second height (H2) at the first distal edge (at 29) of the metalwire (20), where the first height (H1) of the metal wire (20) extendsabove the second height (H2) of the first distal edge (at 29) and theinsulating material (12).

The metal wire (20) comprising a non-planar damascene metal wire (20A,20B, 20C), which may include Cu. The insulating material (12) mayinclude an oxide material, e.g., SiO₂. A coefficient of thermalexpansion of the metal wire (20) may be greater than 10 times thecoefficient of thermal expansion of the insulating material (12). Themetal wire (20) may have a second distal edge (at 29) equal to thesecond height (H2) and a second radius (as shown in FIG. 4A) definedfrom the second height (H2) at the second distal edge (at 29 shown inFIG. 4A) to the first height (H1) at the central portion (C).Additionally, the non-planar damascene metal wire (20) may have alateral length (L) perpendicular to the first height (H1), where thefirst distal edge (at 29) runs along the lateral length (L).

With such features, one or more embodiments herein provide a structureand method of providing the structure that produces a radius where acorner portion of a non-planar metal damascene wire used to be by asecondary soft-pad chemical mechanical planarization process toeliminate the stress riser of the sharp corner portion of the metalinductor formed though a previous fabrication process.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

While only one or a limited number of wiring structures are illustratedin the drawings, those ordinarily skilled in the art would understandthat many different types wiring structures could be simultaneouslyformed with the embodiment herein and the drawings are intended to showsimultaneous formation of multiple different types of wiring structures;however, the drawings have been simplified to only show a limited numberof wiring structures for clarity and to allow the reader to more easilyrecognize the different features illustrated. This is not intended tolimit the embodiments because, as would be understood by thoseordinarily skilled in the art, the embodiments herein are applicable tostructures that include many of each type of structure shown in thedrawings.

In addition, terms such as “right”, “left”, “vertical”, “horizontal”,“top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”,“over”, “overlying”, “parallel”, “perpendicular”, etc., used herein areunderstood to be relative locations as they are oriented and illustratedin the drawings (unless otherwise indicated). Terms such as “touching”,“on”, “in direct contact”, “abutting”, “directly adjacent to”, etc.,mean that at least one element physically contacts another element(without other elements separating the described elements).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of this disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescriptions of the various embodiments of the present invention havebeen presented for purposes of illustration, but are not intended to beexhaustive or limited to the embodiments disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A structure comprising: a metal wire having afirst height at a central portion, a second height at a first distaledge less than said first height, and a radius defined from said secondheight at said first distal edge to said first height at said centralportion; and an insulating material surrounding said metal wire to saidsecond height at said first distal edge of said metal wire, said firstheight of said metal wire extending above said second height of saidfirst distal edge and said insulating material.
 2. The structureaccording to claim 1, said metal wire comprising a non-planar damascenemetal wire.
 3. The structure according to claim 2, said non-planar metalwire comprising Cu.
 4. The structure according to claim 1, saidinsulating material comprising an oxide material.
 5. The structureaccording to claim 4, said oxide material comprising SiO₂.
 6. Thestructure according to claim 1, a coefficient of thermal expansion ofsaid metal wire being greater than 10 times a coefficient of thermalexpansion of said insulating material.
 7. The structure according toclaim 1, said metal wire having a second distal edge equal to saidsecond height and a second radius defined from said second height atsaid second distal edge to said first height at said central portion. 8.A structure comprising: a non-planar damascene metal wire having a firstheight at a central portion, a second height at a first distal edge lessthan said first height, and a radius defined from said second height atsaid first distal edge to said first height at said central portion; andan oxide material surrounding said non-planar damascene metal wire tosaid second height at said first distal edge of said non-planardamascene metal wire, said first height of said non-planar damascenemetal wire extending above said second height of said first distal edgeand said oxide material.
 9. The structure according to claim 8, saidnon-planar damascene metal wire comprising Cu.
 10. The structureaccording to claim 8, said oxide material further comprising SiO₂. 11.The structure according to claim 8, a coefficient of thermal expansionof said non-planar damascene metal wire being greater than 10 times acoefficient of thermal expansion of said oxide material.
 12. Thestructure according to claim 8, said metal wire having a second distaledge equal to said second height and a second radius defined from saidsecond height at said second distal edge to said first height at saidcentral portion.
 13. The structure according to claim 8, said non-planardamascene metal wire having a lateral length perpendicular to said firstheight, said first distal edge running along said lateral length.
 14. Astructure comprising: a non-planar damascene metal wire having a firstheight at a central portion, a second height at a first distal edge lessthan said first height, and a radius defined from said second height atsaid first distal edge to said first height at said central portion; andan insulating material surrounding said non-planar damascene metal wireto said second height at said first distal edge of said non-planardamascene metal wire, said first height of said non-planar damascenemetal wire extending above said second height of said first distal edgeand said insulating material.
 15. The structure according to claim 14,said non-planar damascene metal wire comprising Cu.
 16. The structureaccording to claim 14, said insulating material comprising an oxidematerial.
 17. The structure according to claim 16, said oxide materialcomprising SiO₂.
 18. The structure according to claim 14, a coefficientof thermal expansion of said non-planar damascene metal wire beinggreater than 10 times a coefficient of thermal expansion of saidinsulating material.
 19. The structure according to claim 14, saidnon-planar damascene metal wire having a second distal edge equal tosaid second height and a second radius defined from said second heightat said second distal edge to said first height at said central portion.20. The structure according to claim 14, said non-planar damascene metalwire having a lateral length perpendicular to said first height, saidfirst distal edge running along said lateral length.